Consider an operator facing a high subscriber growth rate. As a
result of this growth rate, the operator faces pressure on its stock
of available public IPv4 addresses. For this reason, the operator
is
motivated to offer IPv6 access as quickly as possible.
The backbone network will be the first part of the operator's
network
to support IPv6. The metro network is not so easily upgraded to
support IPv6 since many devices need to be modified and there may be
some impact to existing services. Thus any means of providing IPv6
access has to minimize the changes required to devices in the metro
network.
In contrast to the situation described for basic 6rd [RFC5569], the
operator is assumed to be unable to manage IP devices on the
customer
premises. As a result, the operator cannot assume that any of these
devices are capable of supporting 6rd.
If the customer equipment is in bridged mode and IPv6 is deployed to
sites via a Service Provider's (SP's) IPv4 network, the IPv6-only
host needs a IPv6 address to visit the IPv6 service. In this
scenario, 6to4 or 6RD can be used. However, each IPv6-only host may
need one corresponding IPv4 address when using 6to4 or 6RD, which
brings great address pressure to the operators.
If the customer equipment is in routing mode, the operator has an
opportunity to avoid assigning IPv4 addresses to sites running IPv6
only. Some other means is available for routing IPv6 traffic
through
the IPv4 network to that site.
This draft talks about "Some other means".
B. R.
Tina
http://tinatsou.weebly.com
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